Why am I getting frame rates less than 2 frames per second for my animations when I have an nVidia GeForce GTX card?
2 frames a second on an animation render is pretty good, considering even most simpler animations + keyframes render at about 1.5-3 seconds a frame are the times most home PC GPU renders get on a render.
If you're sure these are bad frame times, you could try checking if Blender is actually using the GPU to render (if you're running cycles that is):

As others have said, it also depends on what GTX card - There's a big difference between a 1080 and a 1050.
Honestly though, like I said, 2 frames per second on any animation is not bad at all.